Microwave sensing for tissue sealing

ABSTRACT

A system for monitoring the target tissue during a tissue sealing procedure is disclosed. The system includes a forceps having opposing jaw members movable from a first position in spaced relation relative to one another to at least one subsequent position wherein the jaw members cooperate to grasp the tissue therebetween. Each of the jaw members includes a sealing member. The system also includes a generator coupled to the sealing members so that therapeutic energy is delivered to the target tissue. The generator includes an output stage configured to generate therapeutic energy and a microwave detector configured to measure reflected and/or absorbed microwave signals. The monitored microwave signals may be either the therapeutic energy signal or a separate non-therapeutic microwave monitoring signal. The generator also includes a controller operatively coupled to the microwave detector. The controller is configured to determine the state of the tissue based on the reflected and/or absorbed microwave signals and to control the delivery of therapeutic energy from the generator to tissue based on the microwave measurements.

REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patent application Ser. No. 13/205,860, filed on Aug. 9, 2011, now U.S. Pat. No. 8,852,186, the entire contents of which are incorporated by reference herein.

BACKGROUND

Technical Field

The present disclosure relates to forceps for sealing various types of tissue. More particularly, the present disclosure relates to open, laparoscopic or endoscopic forceps for tissue sealing that utilize microwave energy to determine completeness of the tissue seal.

Description of the Related Art

In many surgical procedures, body vessels, e.g., blood vessels, ducts, adhesions, fallopian tubes, etc. are sealed to defunctionalize or close the vessel. Traditionally, staples, clips or sutures have been used to close a body vessel. However, these traditional procedures often leave foreign body material inside a patient. In an effort to reduce foreign body material left within the patient and to more effectively seal the body vessel, energy techniques that seal by heat processes have been employed.

A forceps is particularly useful for sealing tissue and vessels since forceps utilizes mechanical action to constrict, grasp, dissect and/or clamp tissue. Current vessel sealing procedures utilize a unique combination of pressure, gap control and energy to close and seal tissue and body vessels. The combination of heating and applied pressure provides a uniform, controllable seal with minimum collateral damage to body tissue.

SUMMARY

According to one embodiment of the present disclosure, a system for monitoring tissue state during a tissue sealing procedure is disclosed. The system includes a forceps including opposing jaw members movable from a first position in spaced relation relative to one another to at least one subsequent position wherein the jaw members cooperate to grasp tissue therebetween; and a generator coupled to at least one of the jaw members, the generator including: an output stage configured to generate therapeutic energy and non-therapeutic microwave monitoring signals; a microwave detector configured to measure at least one of absorbed or reflected non-therapeutic microwave monitoring signals; and a controller operatively coupled to the microwave detector, the controller configured to determine state of the tissue based on at least one of the absorbed or reflected non-therapeutic microwave monitoring signals and to control the delivery of therapeutic energy from the generator to tissue based the state of the tissue.

According to another embodiment of the present disclosure, a system for monitoring tissue state during a tissue sealing procedure is disclosed. The system includes a forceps including opposing jaw members configured to grasp tissue therebetween, at least one of the jaw members including at least one microwave probe; and a generator coupled to the at least one microwave probe, the generator including: a microwave output stage configured to generate therapeutic microwave energy; a microwave detector configured to measure at least one of absorbed or reflected therapeutic microwave energy; and a controller operatively coupled to the microwave detector, the controller configured to determine state of the tissue based on at least one of the absorbed or the reflected therapeutic microwave energy and to control the delivery of the therapeutic energy from the generator to tissue based the state of the tissue.

A method for monitoring tissue during a tissue sealing procedure is also contemplated by the present disclosure. The method includes the steps of supplying therapeutic energy and non-therapeutic microwave monitoring signals to a forceps, the forceps including opposing jaw members configured to grasp tissue therebetween; measuring reflected non-therapeutic microwave monitoring signals; and controlling the delivery of therapeutic energy based on reflected non-therapeutic microwave monitoring signals.

Another method for monitoring tissue state during a tissue sealing procedure is also contemplated by the present disclosure. The method includes the steps of supplying therapeutic microwave energy to a forceps. The forceps include opposing jaw members configured to grasp tissue therebetween. The method also includes the steps of measuring the reflected and/or absorbed therapeutic microwave signals and controlling the delivery of the therapeutic microwave energy based on reflected and/or absorbed microwave monitoring energy.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure are described herein with reference to the drawings wherein:

FIG. 1 is a perspective view of a tissue sealing system including a forceps and an energy generator according to one embodiment of the present disclosure;

FIG. 2 is a schematic block diagram of a generator according to an embodiment of the present disclosure;

FIG. 3 is a cross-sectional view of a distal end of the forceps of FIG. 1; and

FIG. 4 is a flow chart illustrating a method according to another embodiment of the present disclosure.

DETAILED DESCRIPTION

Various embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Those skilled in the art will understand that the present disclosure may be adapted for use with either an endoscopic instrument or an open instrument; however, different electrical and mechanical connections and considerations apply to each particular type of instrument. The novel aspects with respect to vessel and tissue sealing are generally consistent with respect to both the open and endoscopic designs. In the drawings and in the description that follows, the term “proximal”, as is traditional, will refer to the end of the forceps that is closer to the user, while the term “distal” will refer to the end of the forceps that is further from the user.

Referring now to FIG. 1, a tissue sealing system 2 according to the present disclosure is shown including a forceps 10 coupled to a generator 20. The forceps 10 is adapted to seal tissue using high frequency RF energy or microwave energy. The generator 20 may also be configured to output various types of energy, such as high frequency RF energy (e.g., from about 100 kHz to about 300 MHz) and microwave energy (e.g., from about 300 MHz to about 10,000 MHz).

In one embodiment, the generator 20 includes a microwave detector (e.g., microwave detector 22). The microwave detector 22 is coupled to the forceps 10 and is configured to determine progression of the sealing process based on measurements of microwave energy reflected and absorbed by the tissue. Microwave energy of either non-therapeutic or therapeutic type is supplied to the tissue grasped by the forceps 10.

As used herein the term “therapeutic” denotes RF or microwave energy applied to the tissue for treating tissue. In particular, therapeutic energy denotes sufficient energy for increasing the temperature of the tissue and to cause thermodynamically irreversible processes to occur therein. As used herein, the term “non-therapeutic” denotes microwave measurement signals that are intended only to measure tissue properties and generally provide little to no therapeutic effect on the tissue. Since the total energy delivered to the tissue by a therapeutic or non-therapeutic signal depends on the rate of energy deposition into the tissue as well as on the duration of the signal, the distinction between therapeutic and non-therapeutic signals is due to the power of the signal, the duration of the signal, and the efficiency with which the signal is coupled to the tissue (e.g., a high power signal may cause very little heating if only a small fraction of the power in the signal is absorbed by the tissue). In embodiments, non-therapeutic signals may provide from about 0.1% to about 10% of the total energy supplied to the tissue by therapeutic signals.

Generally, the present disclosure provides a system and method for microwave monitoring of tissue during a tissue sealing procedure, by measuring or monitoring the interaction of a microwave signal with the target tissue. Measurements might include reflection from and/or absorption of microwave energy by the tissue. Processing of the measurements allows a more accurate analysis of how the tissue is transformed during the fusion/sealing process. Such an analysis provides for improved tracking of the tissue modifications that lead to high quality seals. The processed data obtained during the fusion process may be incorporated into a suitable feedback loop controlling the delivery of energy (e.g., RF or microwave) to the tissue so that the optimum tissue transformations are obtained.

In one embodiment, the interaction of a therapeutic microwave signal with the target tissue can be monitored. In another embodiment, non-therapeutic microwave monitoring signals may be applied either simultaneously with the therapeutic energy or be interleaved therewith. The measured signal interaction (or the changes therein) may then be used as a control parameter in a tissue sealing algorithm to control energy delivery.

Without being constrained by any particular theory, it is believed that dehydration of the target tissue is an important part of transforming the target tissue into a strong seal. Electromagnetic radiation at microwave frequencies interacts with tissue primarily through the water contained in the tissue. This makes microwave techniques very sensitive to the amount of water contain in the tissue (e.g., the hydration of the tissue). Since microwave energy can also be used to heat tissue containing water, microwave based monitoring of the target tissue can potentially utilize the same transmission structures used to transport the therapeutic microwave signal to the target tissue.

FIG. 2 shows a schematic block diagram of the generator 20. The generator 20 includes a controller 24, and an output stage 23. The controller 24 includes a microprocessor 25 operably connected to a memory 26, which may be volatile type memory (e.g., RAM) and/or non-volatile type memory (e.g., flash media, disk media, etc.). The controller 24 includes an output port that is operably connected to the output stage 23 allowing the microprocessor 25 to control the output of the generator 20 according to either open and/or closed control loop schemes. Those skilled in the art will appreciate that the microprocessor 25 may be substituted by any logic processor (e.g., control circuit) adapted to perform the control function discussed herein.

In a closed loop control scheme, a plurality of sensors measure a variety of tissue and energy properties (e.g., tissue impedance, tissue temperature, output current and/or voltage, reflected energy, absorbed energy, etc.), and provide feedback to the controller 24. The controller 24 then signals the output stage 23, which then adjusts the output power. The controller 24 also receives input signals from the input controls of the generator 20. The controller 24 utilizes the input signals to adjust power output by the generator 20 and/or performs other control functions thereon.

The therapeutic energy delivered to and applied to the tissue by the forceps 10 may be either RF or microwave energy or other forms that result in heating of the tissue. The forceps 10 is coupled to the generator 20 via a cable 11 adapted to transmit energy and control signals therebetween.

The forceps 10 is configured to support an end effector assembly 100. Forceps 10 typically includes various conventional features (e.g., a housing 60, a handle assembly 75, a rotating assembly 80, a trigger assembly 70) that enable forceps 10 and end effector assembly 100 to mutually cooperate to grasp, seal and, if warranted, divide tissue. Forceps 10 generally includes housing 60 and handle assembly 75, which includes moveable handle 62 and handle 72 that is integral with housing 60. Handle 62 is moveable relative to handle 72 to actuate end effector assembly 100 to grasp and treat tissue. Forceps 10 also includes a shaft 12 having a distal end 14 and a proximal end 16. The shaft 12 mechanically engages the end effector assembly 100 at its distal end 14 and the rotating assembly 80 and the housing 60 at its proximal end 16. Movement of rotating assembly 80 imparts similar rotational movement to shaft 12 which, in turn, rotates end effector assembly 100.

Referring to FIG. 3, the end effector assembly 100 includes two jaw members 110 and 120 having proximal ends 111, 121 and distal ends 113, 123. Jaw members 110 and 120 are pivotable about a post 160 and are movable from a first position wherein jaw members 110 and 120 are spaced relative to another, to a second position wherein jaw members 110 and 120 are closed and cooperate to grasp tissue therebetween. As discussed in more detail below, the end effector assembly 100 may be adapted for use with various energy sources.

The shaft 12 houses a pushrod 101 that is operatively coupled to the movable handle 62 such that when the handle 62 is moved relative to the handle 72 the pushrod 101 moves longitudinally, either proximally or distally within the shaft 12. The pushrod 101 includes a push pin 103 disposed at the distal end 16 of shaft 12. Each of the jaw members 110 and 120 includes a slot 105 and 107, respectively, disposed at the proximal ends thereof. The slots 105 and 107 are in mechanical cooperation with the push pin 103, which is adapted to move within the slots 105 and 107. The pin 103 and slots 105 and 107 operate as a cam-follower mechanical linkage. Motion of the pushrod 101 causes the pin 103 to slide within respective slots 105 and 107. The slots 105 and 107 may be angled with respect to the distal ends of the jaws members 110 and 120 such that the members 110 and 120 move either toward or away from each other as the pushrod 101 is moved longitudinally in a proximal or distal direction, respectively.

The forceps 10 also includes a trigger assembly 70 that advances a knife 200 disposed within the end effector assembly 100. Once a tissue seal is formed, the user activates the trigger assembly 70 to separate the tissue along the tissue seal. Knife 200 includes a sharpened edge 205 for severing the tissue held between the jaw members 110 and 120 at the tissue sealing site.

Each jaw member 110 and 120 includes a sealing member 112 and 122, respectively, disposed on an inner-facing surface and/or within the jaw members 110 and 120. Sealing members 112 and 122 cooperate to seal tissue held between the jaw members 110 and 120 upon the application of energy. At least one of the sealing members 112 and 122 is connected to generator 20 that delivers energy to the tissue held therebetween.

In RF energy application, one or more of the sealing members 112 and 122 may be configured as electrosurgical electrodes that may be formed from one or more electrically conductive plates suitable for conducting RF energy to the tissue. The sealing members 112 and 122 are disposed on the inner-facing surfaces of the jaw members 110 and 120. More specifically, the cable 11 may couple the sealing members 112 and 122 to the generator and may be internally divided into one or more cable leads (not explicitly shown) that are designed to transmit electrical currents through their respective feed paths through the forceps 10 to the end effector assembly 100 such that energy is transmitted from the various cable leads to the respective feed paths and energy is transmitted to the tissue.

In microwave application, the sealing members 112 and 122 are configured as one or more microwave probes. In microwave energy application, the sealing members 112 and 122 may be disposed on the inner-facing surfaces or within the jaw members 110 and 120. The microwave probes are coupled to the generator 20, which is adapted to supply microwave energy to the forceps 10 through the cable 11, which may be configured as a coaxial cable suitable for delivery of microwave energy. The coaxial cable connects one or more of the microwave probes to the generator 20.

During operation tissue is grasped between the sealing members 110 and 120 and the generator 20 applies either RF or microwave energy thereto to seal the tissue. The output stage 23 also generates microwave monitoring signals that are transmitted to the target tissue. The output stage 23 may be an adjustable microwave signal generator capable of providing microwave signals in the range of 300 MHz to about 10,000 MHz, at signal power levels of up to 200 W. The output stage 23 is adjusted to provide the microwave monitoring and/or heating of the target tissue.

In one embodiment, the output stage 23 generates the microwave monitoring signals intermittently, interleaving the non-therapeutic microwave signals with therapeutic energy. If therapeutic RF energy is used in conjunction with microwave non-therapeutic signals, the output stage 23 may include two or more output stages to provide one output stage for therapeutic energy and another for the monitoring signals. In another embodiment, the output stage 23 may supply microwave monitoring signals continuously and simultaneously with the microwave therapeutic signals. In a further embodiment, if microwave energy is supplied therapeutically, the therapeutic signal may also be used as monitoring a signal.

Microwave energy delivered to the tissue is typically either absorbed by the tissue or reflected back to the generator 20. The microwave detector 22 is configured to determined absorbed microwave energy based on the measured reflected and/or absorbed microwave energy. Absorbed microwave energy may be determined by subtracting measured reflected energy from the total incident energy supplied by the generator 20. The amount of microwave energy absorbed by the tissue depends on the hydration of the tissue and the amount and geometry of the tissue within the jaws.

The output and reflected microwave signals are measured with the microwave detector 22. The measured amplitude of the output and reflected microwave signals are then transmitted to the controller 24 which analyzes the amplitudes over time to determine the current state of the target tissue including, but not limited to, desiccation, hydration, impedance, and combinations thereof, and/or the appropriate response of the tissue sealing system. The controller 24 is also programmed or otherwise configured to adjust the therapeutic energy of the generator 20 based on the measured state of the target tissue.

The microwave detector 22 may be tunable to a selected band of frequencies in the microwave range, more particularly, in the frequency range of the reflected and/or absorbed microwave monitoring signals. The measured monitoring signals are then transmitted to the controller 24, which then analyzes the signals to determine the completeness of the seal. The controller 24 is also programmed or otherwise configured to adjust the therapeutic energy of the generator 20 based on the detected seal parameters.

FIG. 4 illustrates a method for controlling a sealing procedure based on the state of the tissue as measured by the microwave monitoring signals. The method may be implemented as an algorithm that controls the power applied to the tissue by the generator 20 and the forceps 10, so that a completed seal is achieved. The algorithm may be embodied as any type of suitable machine-readable code stored in the memory 26 and executable by the controller 24 and/or the microprocessor 25.

Many different possible control algorithms may exist, and therefore the example described below is intended to be illustrative rather than exclusive. In step 100, the output stage 23 transmits an initial non-therapeutic microwave monitoring signals. The monitoring signals may be supplied at varying intensities and microwave frequencies. The response of the tissue-jaw system is measured and recorded.

In step 102, the state of the tissue is estimated based on the measured response of the tissue-jaw system. If the seal is complete, step 104 directs the algorithm to terminate. If the seal is not complete, step 106 is executed. In step 106, a new therapeutic power level is determined. Then, in step 108, the new therapeutic signal is applied. At this point, a new control cycle begins with the application of the microwave monitoring signals, step 100. Many variations of this algorithm may be realized including variants such as, where the therapeutic and monitoring signals are applied simultaneously and/or continuously, where the therapeutic signal is used as the monitoring signal, and the like.

While several embodiments of the disclosure have been shown in the drawings and/or discussed herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto. 

What is claimed is:
 1. A system for treating tissue comprising: a microwave probe; and a generator coupled to the microwave probe, the generator including: an output stage configured to generate therapeutic energy and non-therapeutic microwave monitoring signals; a microwave detector configured to measure at least one of absorbed or reflected non-therapeutic microwave monitoring signals, the microwave detector being tunable to a selected frequency band in a frequency range of the non-therapeutic microwave monitoring signals; and a controller operatively coupled to the microwave detector, the controller configured to determine at least one property of tissue based on at least one of the measured absorbed or reflected non-therapeutic microwave monitoring signals and to control delivery of therapeutic energy from the generator to tissue based on the at least one property.
 2. The system according to claim 1, wherein the microwave detector is configured to measure absorption of non-therapeutic microwave monitoring signals.
 3. The system according to claim 1, wherein the output stage is configured to interleave non-therapeutic microwave monitoring signals with therapeutic energy.
 4. The system according to claim 1, wherein the output stage is configured to generate non-therapeutic microwave monitoring signals simultaneously with therapeutic energy.
 5. The system according to claim 1, wherein the output stage is configured to generate therapeutic energy selected from the group consisting of high frequency RF energy from about 100 kHz to about 300 MHz and microwave energy from about 300 MHz to about 10,000 MHz.
 6. A generator for treating tissue, the generator comprising: an output stage configured to generate therapeutic energy and non-therapeutic microwave monitoring signals; a microwave detector configured to measure at least one of absorbed or reflected non-therapeutic microwave monitoring signals, the microwave detector being tunable to a selected frequency band in a frequency range of the non-therapeutic microwave monitoring signals; and a controller operatively coupled to the microwave detector, the controller configured to determine at least one property of tissue based on at least one of the measured absorbed or reflected non-therapeutic microwave monitoring signals and to control delivery of therapeutic energy from the generator to tissue based on the at least one property.
 7. The generator according to claim 6, wherein the microwave detector is configured to measure absorption of non-therapeutic microwave monitoring signals.
 8. The generator according to claim 6, wherein the output stage is configured to interleave non-therapeutic microwave monitoring signals with therapeutic energy.
 9. The generator according to claim 6, wherein the output stage is configured to generate non-therapeutic microwave monitoring signals simultaneously with therapeutic energy.
 10. The generator according to claim 6, wherein the output stage is configured to generate therapeutic energy selected from the group consisting of high frequency RF energy from about 100 kHz to about 300 MHz and microwave energy from about 300 MHz to about 10,000 MHz.
 11. A method for treating tissue, the method comprising: delivering therapeutic energy and non-therapeutic microwave monitoring signals to a microwave probe; tuning a microwave detector to a selected frequency band in a frequency range of the non-therapeutic microwave monitoring signals; measuring reflected non-therapeutic microwave monitoring signals; and controlling the delivery of therapeutic energy based on the measured reflected non-therapeutic microwave monitoring signals.
 12. The method according to claim 11, further comprising measuring absorption of non-therapeutic microwave monitoring signals.
 13. The method according to claim 11, wherein supplying therapeutic energy and non-therapeutic microwave monitoring signals to a microwave probe further includes interleaving non-therapeutic microwave monitoring signals with therapeutic energy.
 14. The method according to claim 11, wherein supplying therapeutic energy and non-therapeutic microwave monitoring signals to a microwave probe further includes generating non-therapeutic microwave monitoring signals simultaneously with therapeutic energy.
 15. The method according to claim 11, wherein supplying therapeutic energy and non-therapeutic microwave monitoring signals to a microwave probe further includes generating therapeutic energy selected from the group consisting of high frequency RF energy from about 100 kHz to about 300 MHz and microwave energy from about 300 MHz to about 10,000 MHz. 